如何实现控制中心交互式解除动画

Question

我目前正在尝试复制iOS控制面板的解散交互。到目前为止，我只能通过向下滑动来解散视图。我向上滑动时无法复制相同的弹性，向上滑动后向下滑动或通常只是在播放视图时无法复制平滑过渡。

这是我在视图中的handlePan处理程序，我试图解雇：

func handlePan(recognizer: UIPanGestureRecognizer) {
    let translation = recognizer.translation(in: self)

    switch recognizer.state {
    case .began:

        self._displayPosition = self.frame
        self._dismissAnimator = UIViewPropertyAnimator(duration: 0.75, curve: .easeOut)

        self._dismissAnimator.pauseAnimation()
    case .changed:
        if translation.y < 0 {
            self._dismissAnimator.addAnimations {
                self.frame = self._displayPosition.offsetBy(dx: 0, dy: -20)
            }
            self._dismissAnimator.fractionComplete = -translation.y*0.10/20
        } else {
            self._dismissAnimator.addAnimations {
                self.frame = self._displayPosition.offsetBy(dx: 0, dy: self._offsetFromScreenBottom)
            }
            self._dismissAnimator.fractionComplete = translation.y / self._offsetFromScreenBottom
        }

    case .ended:
        if self.frame.origin.y < self._displayPosition.origin.y {
            self._dismissAnimator.stopAnimation(true)
            self._dismissAnimator.addAnimations {
                self.frame = self._displayPosition
            }
            self._dismissAnimator.startAnimation()
        } else {
            self._dismissAnimator.continueAnimation(withTimingParameters: nil, durationFactor: 0)
        }
    default:
        self._dismissAnimator.finishAnimation(at: .start)
    }
}

提前致谢！